Gadolinium-enhanced MRI with dynamic evaluation in diagnosing the local recurrence of rectal cancer

At early stages, the diagnosis of local recurrence of rectal cancer is often difficult and magnetic resonance imaging (MRI) is currently considered the most accurate method for diagnosing recurrence. We evaluated the role of unhenhanced and gadolinium-enhanced MRI for the diagnosis of local recurrence of rectal cancer.

Thirty-six patients, suspected of having a pelvic recurrence of rectal cancer, were evaluated by a high field strength MRI unit. Unenhanced spin-echo T1- and T2-weighted sequences and gadolinium-enhanced dynamic fast multiplanar spoiled gradient recalled sequences were performed in all patients. The dynamic images were re-elaborated with semiquantitative postprocessing by plotting intensity-time curves and calculating the percentage of signal increase at the end of the first postcontrast dynamic sequence. The pelvic lesions were classified as recurrent or not recurrent by applying the following diagnostic criteria: (a) morphology and signal intensity of the lesion in unenhanced sequences and (b) percentage of enhancement in dynamic enhanced sequences. Diagnosis was confirmed by computed tomography-guided needle biopsy (12 patients), surgery (four patients), clinical and imaging follow-up (20 patients).

The diagnosis was local recurrence in 15 patients and noncancerous lesions in 21 patients. Unenhanced MRI had 80% sensitivity and 86% specificity. Analysis of the percentage of enhancement showed 87% sensitivity and 100% specificity.

In agreement with the literature, our results showed a high sensitivity and specificity for dynamic MRI. This technique thus can be considered an important adjunct to unenhanced MRI, especially in selected cases in which unenhanced MRI cannot rule out local recurrences. However, these results must be validated by further investigations.